Vehicle air conditioner in which shaft seal is protected

ABSTRACT

An object of the present invention is to protect a shaft seal of a variable displacement compressor of an air conditioner for a vehicle by the control thereof. The air conditioner for a vehicle comprises a variable displacement swash plate type compressor for compressing a refrigerant and a control unit for controlling the compressor. The compressor is driven by an engine of a vehicle and is normally connected to the engine at all times. The control unit controls the compressor such that when the compressor is in an off state the compressor turns on and operates at predetermined time intervals of 10 minutes and for one minute, and the revolution speed of the compressor is equal to or higher than predetermined 6,000 rpm.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air conditioner for a vehicle and, particularly, to a compressor of an air conditioner for a vehicle and, more particularly, to control of a variable displacement compressor of an air conditioner.

2. Description of the Related Art

Some vehicle air conditioners comprise a variable displacement compressor. A variable displacement compressor is capable of properly changing its displacement in accordance with the load of an air conditioner, the operating state of a vehicle, etc., and has various advantages such as in temperature control, energy saving effect, etc. Further, a variable displacement compressor may be directly connected to an engine, which is the drive unit of a compressor and there is no need for it to be connected via a clutch etc. and, therefore, the number of parts can be reduced and is more advantageous in cost compared to the case where a fixed displacement compressor is used.

As a variable displacement compressor, a swash plate type is used widely. FIG. 1 shows a general structure of a variable displacement swash plate type compressor 10. The compressor 10 comprises a shaft 20 rotatably driven by an engine (not shown). The displacement of the compressor 10 is controlled by a control valve 42. To the control valve 42, pressure in a swash plate chamber 15 is introduced and the swash plate chamber 15 serves as a suction path of a refrigerant. As a refrigerant is introduced into the swash plate chamber 15, the shaft 20 is sealed with a shaft seal 19 and the refrigerant is prevented from leaking out of the compressor 10. The shaft 20 and the shaft seal 19 slide relatively and oil for lubrication is contained in the refrigerant flowing into the swash plate chamber 15 and, therefore, when the refrigerant reaches the shaft seal 19, the shaft seal 19 is lubricated by the oil. In FIG. 1 and FIG. 2, the flow of the oil is shown by the arrow. In general, the configuration of the variable displacement swash plate type compressor described above is well known.

In the prior art, there was a proposal regarding the structure of the shaft seal 19 (for example, refer to patent document 1). The structure of such a shaft seal is already known. In the prior art, when a vehicle is in operation and the compressor is off, the flow of the oil shown in FIG. 1 and FIG. 2 becomes unsmooth and then, in particular, when the revolution speed of the engine becomes high, the pressure around the shaft seal becomes high, resulting in severe conditions to the shaft seal. Such conditions adversely affect the durability of the shaft seal and as a result, increase the possibility that a problem of seal defect at the shaft etc. arises.

As describe above, when the compressor is in the off state and the revolution speed of the engine is high, the shaft seal is adversely affected because the temperature and the pressure around the shaft seal rise.

The wording “a state in which a compressor is off” in this specification means a state in which the flow rate of the refrigerant flowing through the air conditioner cycle is almost zero.

[Patent document 1] Japanese Unexamined Patent Publication (Kokai) No. 2002-364759

SUMMARY OF THE INVENTION

The present invention has been developed with the above-problems being taken into account, and an object thereof is to provide a compressor having a configuration for protecting a shaft seal and, more particularly, a variable displacement compressor for an air conditioner of a vehicle.

Another object of the present invention is to provide a control method capable of protecting a shaft seal of a compressor and, more particularly, of a variable displacement compressor for an air conditioner of a vehicle.

In order to attain the above-mentioned objects, in a first aspect of the present invention, an air conditioner comprises a variable displacement compressor for compressing a refrigerant and a control unit for controlling the compressor. The compressor is driven by an engine of a vehicle and is normally connected to the engine at all times. The control unit is characterized by controlling the compressor such that when the compressor is in an off state the compressor turns on and operates at predetermined time intervals T1 and intermittently (temporarily) during time T2, and the revolution speed thereof is equal to or higher than a predetermined revolution speed N.

With such a configuration, when a vehicle is in high-speed operation and the compressor is in the off state, during which the shaft seal of the variable displacement compressor of an air conditioner for a vehicle is adversely affected, the shaft seal is protected and therefore the compressor is protected as a result by turning on the compressor at predetermined time intervals and intermittently (temporarily).

A second aspect of the present invention, according to the above-mentioned first aspect, is characterized in that the compressor is a swash plate type.

According to the present aspect, the type of the compressor of the present invention is made more concrete.

A third aspect of the present invention according to either of the above-mentioned first and second aspects, is characterized in that the control unit preferably controls the compressor such that the compressor turns on and operates at the time intervals T1 being substantially equal to or longer than one minute and for the time T2 being substantially equal to or longer than one minute when the compressor is in the off state and the revolution speed of the compressor is equal to or higher than a predetermined revolution speed N, and that it is more preferable to control the compressor such that the compressor turns on and operates at the time intervals T1 being substantially equal to or longer than 10 minutes and for the time T2 being substantially equal to one minute.

According to the present aspect, an aspect is disclosed in which the control parameters of an air conditioner for a vehicle according to the present invention are made more concrete.

A fourth aspect of the present invention according to any one of the above-mentioned first to third aspects, is characterized in that the predetermined revolution speed N of the compressor is preferably substantially 6,000 rpm.

According to the present aspect, the revolution speed of the compressor, which is a control parameter of the compressor of an air conditioner for a vehicle according to the present invention, is made more concrete.

In a method for controlling an air conditioner for a vehicle according to a fifth aspect of the present invention, the air conditioner comprises a variable displacement compressor for compressing a refrigerant and a control unit for controlling the compressor. The control method is carried out by the control unit and the compressor of the air conditioner is driven by an engine of a vehicle and is normally connected to the engine at all times. The method for controlling an air conditioner for a vehicle is characterized by comprising the steps of: checking whether the revolution speed of the compressor is equal to or higher than a predetermined revolution speed N; checking whether the compressor is off; and turning on and operating the compressor at predetermined time intervals T1 and intermittently (temporarily) during time T2 when the compressor is in the off state, and the revolution speed of the compressor is equal to or higher than the predetermined revolution speed N.

With such a control method, when a vehicle is in high-speed operation and the compressor is in the off state, during which the shaft seal of the variable displacement compressor of an air conditioner for a vehicle is adversely affected, the shaft seal is protected and, therefore, the compressor is protected as a result by turning on the compressor at predetermined time intervals and intermittently (temporarily).

A sixth aspect of the present invention according to the above-mentioned fifth aspect, is characterized in that the compressor is a swash plate type.

According to the present aspect, the type of the compressor of the present invention is made more concrete.

In a seventh aspect of the present invention according to either of the above-mentioned fifth and sixth aspects, the control method is characterized in that it is preferable to control the compressor such that the compressor turns on and operates at the time intervals T1 being substantially equal to or longer than one minute and for the time T2 being substantially equal to or longer than one minute when the compressor is in the off state and the revolution speed of the compressor is equal to or higher than the predetermined revolution speed N, and that it is more preferable to control the compressor such that the compressor turns on and operates at the time intervals T1 which are substantially equal to or longer than 10 minutes and for the time T2 which are substantially equal to one minute.

According to the present aspect, an aspect is disclosed in which the control parameters of an air conditioner for a vehicle according to the present invention are made more concrete.

An eighth aspect of the present invention according to any one of the above-mentioned fifth to seventh aspects, is characterized in that the predetermined revolution speed N of the compressor is preferably substantially 6,000 rpm.

According to the present aspect, the revolution speed of the compressor, which is the control parameter of the compressor of an air conditioner for a vehicle according to the present invention, is made more concrete.

The present invention may be more fully understood from the description of the preferred embodiments of the invention set forth below, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a cross-sectional view showing a general structure of a variable capacity swash plate type compressor of an air conditioner for a vehicle according to an embodiment of the present invention.

FIG. 2 is a detail view of the A part, which is at a shaft seal of the compressor in FIG. 1.

FIG. 3 is a diagram for generally explaining a configuration of a control system in an embodiment of an air conditioner according to the present invention.

FIG. 4 is a flow chart for explaining a control of an air conditioner for a vehicle in an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An air conditioner for a vehicle in an embodiment of the present invention is explained in detail based on drawings. FIG. 3 and FIG. 4 explain a control system in an embodiment of an air conditioner for a vehicle according to the present invention, wherein FIG. 3 is a diagram for generally explaining a configuration of a control system in an embodiment of the present invention and FIG. 4 is a flow chart for explaining a control in an embodiment of the present invention.

An air conditioner for a vehicle 1 in an embodiment of the present invention comprises a variable displacement swash plate type compressor 10 shown in FIG. 1 and FIG. 2. As the structure of the compressor 10 has already been explained, an explanation is omitted here.

First, the outline of the control of an air conditioner is explained with reference to FIG. 3. The air conditioner 1 is controlled by a vehicle control unit (ECU) 4 and, in the present embodiment, the ECU 4 includes control to protect a shaft seal 19 of the compressor 10. The vehicle control unit (ECU) 4 calculates the revolution speed of the compressor 10 from the input revolution speed of an engine. The state of the compressor 10 (ON or OFF) is also input to the ECU 4. When the revolution speed of the compressor 10 is high and the compressor 10 is in the off (OFF) state, the engine (not shown) and the compressor 10 are connected with each other and a shaft 20 of the compressor 10 is revolving at a high-speed. On the other hand, as the compressor 10 is off at this time, the refrigerant including lubrication oil is not supplied to the shaft seal 19 and therefore the shaft seal 19 is in a poor lubrication state. Therefore, the ECU 4 lubricates and protects the shaft seal 19 of the compressor 10 by controlling a control target 3 of the compressor 10, that is, for example, a control valve 42, such that the compressor turns on (ON) intermittently (temporarily). When the compressor turns on, as a difference in pressure is produced between the discharge side and the crank chamber, the oil and the refrigerant are guided to the shaft seal whereby the shaft seal is lubricated.

Next, the control of the air conditioner 1 in the present embodiment is explained in detail with reference to FIG. 4. In step 40 (S10), when the present control system is turned on, the flow proceeds to step 20 (S20). In step 20, the revolution speed N of the compressor 10 is checked. In the present embodiment, it is preferable for the revolution speed N of the compressor to be 6,000 rpm. When N is equal to or higher than 6,000 rpm (YES), the flow proceeds to step 30 (S30). In step 30, whether the compressor 10 is on or off is checked. When the compressor 10 is off (NO), the flow proceeds to step 40 (S40). In step 40, the compressor 10 is intermittently (temporarily) turned on for the predetermined time T1. In the present embodiment, it is preferable for T1 to be substantially one minute.

When one minute of the time T1, during which the compressor 10 is on, elapses, the flow proceeds to step 50 (S50). In step 50, whether another compressor-on command, for example, a command to turn on an air conditioner, is issued, is checked. If a compressor-on command is not issued (NO), the flow proceeds to step 60 (S60). In step 60, the time T2, during which the compressor 10 is off, is checked. In the present embodiment, it is preferable for T2 to be substantially 10 minutes. If 10 minutes of T2 have not elapsed yet, the flow returns to step 50 and a compressor-on command is checked. If 10 minutes of T2 elapse in a state in which there is no compressor-on command, the flow returns to step 20 and the flow is repeated again from step 20. In this manner, the shaft seal 19 of the compressor 10 is lubricated and protected by turning on (ON) the compressor 10 periodically and intermittently (temporarily) when the revolution speed of the compressor 10 is high (equal to or higher than N) and the compressor is in the off state.

In the control flow in FIG. 4 described above, in step 20, when the revolution speed of the compressor is lower than N (when NO), that is 6,000 rpm in the present embodiment, the flow proceeds to step 11. In step 11, the current state of the compressor 10 is maintained. After this, the flow proceeds to step 20 and the same control flow is repeated. In step 30, when the compressor 10 is on (YES), the flow also proceeds to step 11. In step 50, when a compressor-on command is issued (YES), the flow proceeds to step 51. In step 51, an operation mode of the compressor such as the operation of the air conditioner 1 etc. is carried out.

In the above-mentioned explanation, the revolution speed N of the compressor is assumed to be 6,000 rpm, however, this value is determined properly depending on the type, capacity, etc., of the compressor and in this explanation, this value is suited to a specific concrete example and it is just an example to make the explanation easier to understand. Further, it will be apparent to those skilled in the art that the times T1 and T2 used in control may have a certain range. For example, T1 may be longer, such as two minutes, provided it is not shorter than one minute, however, one minute is more efficient and suitable. T2 may be longer provided it is not shorter than one minute, however, 10 minutes are more efficient and suitable. Further, T1 and T2 are determined properly depending on the specifications etc. of the compressor and it will be apparent to those skilled in the art that the suitable values should be changed depending on the type of the compressor, the type of the vehicle, etc. The concrete numerical values in the above-mentioned embodiments are suited to specific concrete examples and they are just examples to make the explanation easier to understand.

Next, the effects and functions of the above-mentioned embodiments are explained.

The following effect can be expected from the air conditioner in the above-mentioned embodiments of the present invention.

When the vehicle is in high-speed operation and the compressor is in the off state, during which the shaft seal of the variable displacement compressor of an air conditioner for a vehicle is adversely affected, the shaft seal is protected and therefore the compressor is protected as a result by turning on the compressor at fixed time intervals and intermittently (temporarily).

In the embodiments described above or shown in the accompanying drawings, the compressor of an air conditioner for a vehicle according to the present invention is explained as a swash plate type, however, the present invention is not limited to this and the present invention may be applied to a variable capacity compressor other than one of the swash plate type. In this case, the control target in the above-mentioned explanation is the control valve 42 of the compressor, however, the control target may be also changed, from the control valve 42, in accordance with the type of the target compressor.

In the above-mentioned explanation, the control of the present invention is incorporated in the vehicle control unit (ECU) and the control is carried out by the ECU, however, it may also be possible to incorporate the control of the present invention in another control unit other than the ECU and carry out the control thereby.

As described in the above-mentioned explanation, the control of the present invention is incorporated as part of the control of an air conditioner for a vehicle and, therefore, it may also be possible that the control procedure for another air conditioner, compressor, vehicle, etc., is incorporated in or added to the control flow in the above-mentioned embodiments and elements required for the control of an air conditioner or a compressor are incorporated.

The above-mentioned embodiments are only examples of the present invention and the present invention is not limited by the embodiments but is specified only by the claims described hereinafter, and embodiments other than the above-mentioned embodiments are also possible.

While the invention has been described by reference to specific embodiments chosen for the purposes of illustration, it should be apparent that numerous modifications could be made thereto, by those skilled in the art, without departing from the basic concept and scope of the invention. 

1. An air conditioner for a vehicle, comprising: a variable displacement compressor for compressing a refrigerant; and a control unit for controlling the compressor, wherein: the compressor is driven by an engine of a vehicle and is normally connected to the engine at all times; and the control unit controls the compressor such that when the compressor is in an off state the compressor turns on and operates at predetermined time intervals T1 and intermittently during time T2 and a revolution speed of the compressor is equal to or higher than a predetermined revolution speed N.
 2. The air conditioner as set forth in claim 1, wherein the compressor is a swash plate type.
 3. The air conditioner as set forth in claim 1, wherein it is preferable for the control unit to control the compressor such that the compressor turns on and operates at the time intervals T1 substantially equal to or longer than one minute and for the time T2 substantially equal to or longer than one minute when the compressor is in the off state and the revolution speed of the compressor is equal to or higher than a predetermined revolution speed N, and it is more preferable to control the compressor such that the compressor turns on and operates at the time intervals T1 substantially equal to or longer than ten minutes and for the time T2 of substantially one minute.
 4. The air conditioner as set forth in claim 1, wherein preferably the predetermined revolution speed N of the compressor is substantially 6,000 rpm.
 5. A method for controlling an air conditioner for a vehicle comprising a variable displacement compressor for compressing a refrigerant and a control unit for controlling the compressor, wherein the control method is carried out by the control unit, the compressor being driven by an engine of a vehicle and normally connected to the engine at all times, and wherein the control method comprises: a step for checking whether the revolution speed of the compressor is equal to or higher than a predetermined revolution speed N; a step for checking whether the compressor is off; and a step for turning on and operating the compressor at predetermined time intervals T1 and intermittently during time T2 when the compressor is in an off state, and revolution speed of the compressor is equal to or higher than a predetermined revolution speed N.
 6. The control method as set forth in claim 5, wherein the compressor is a swash plate type.
 7. The control method as set forth in claim 5, wherein it is preferable for the control unit to control the compressor such that the compressor turns on and operates at the time intervals T1 substantially equal to or longer than one minute and for the time T2 substantially equal to or longer than one minute when the compressor is in an off state and the revolution speed of the compressor is equal to or higher than the predetermined revolution speed N, and it is more preferable to control the compressor such that the compressor turns on and operates at the time intervals T1 substantially equal to or longer than ten minutes and for the time T2 of substantially one minute.
 8. The control method as set forth in claim 5, wherein preferably the predetermined revolution speed N of the compressor is substantially 6,000 rpm. 